1. Field of the Invention
This invention relates generally to an apparatus for recording and/or reproducing a control signal, and more particularly to an apparatus of this kind which is capable of exactly recording a control signal in a specific area of a recording medium.
2. Description of the Prior Art
There is known a digital audio tape recorder (R-DAT) which uses a rotary head for recording an audio signal on a tape as a PCM signal. When an audio signal or other information is recorded by such a digital audio tape recorder, recorded on the medium is not only the PCM-coded audio signal but also a sub-code which includes positional information, such as a program number, a time code and so on and other required auxiliary data, e.g., a program start identifying signal, a skip identifying signal and so on. It is therefore possible to know, on the basis of the sub-code, a tape position and detect the start point of a program in a search mode when the signal is reproduced.
The assignee of the present invention has proposed a method of recording a program start identifying signal in U.S. Pat. No. 4,641,208. According to this method, a program start identifying signal "1" is recorded only in a leading portion of a program. At the middle part of the program, the program, the program start identifying signal "0" is recorded. In the first recording, a program number is sequentially recorded in a predetermined location of the sub-code area of each program. However, in the second recording or afterward, a program start identifying signal is recorded in place of the program number in the above predetermined location for a time period required for detection, e.g. for 9 seconds. When program numbers are recorded on a tape which has all programs recorded thereon, the program start identifying signals are sequentially detected in the respective programs, and a program number following the last one designated in the first recording is sequentially recorded in the same portion in which the program start identifying signal is recorded for the respective programs.
According to the above-mentioned recording method, when the program start identifying signal is recorded, if a desired position at which the program start identifying signal is desired to be recorded arrives, it is recorded by depressing a particular button assigned for this operation. However, due to a delay in the response of the operator and so on, there may occur the problem that the program start identifying signal is recorded at a position slightly deviated from the desired position, thereby causing the top portion of a program to be cut, for example, upon the search operation.
To attend to the above-mentioned defect, the assignee of the present invention has proposed a recording and/or reproducing apparatus which can always record a control signal, such as the program start identifying signal, exactly at a desired position by repeatedly reproducing the control signal.
A skip identifying signal is a control signal which is recorded in the sub-code portion. This skip identifying signal is usually "0", but skip identifying signal "1" is recorded for approximately 1 second in a head portion of a specific unnecessary information portion which is desired to be skipped upon reproducing a program. A method of recording the skip identifying signal is disclosed in U.S. patent application Ser. No. 858,023, filed on May 29, 1985.
Among these control signals, the program start identifying signal "1" and the skip identifying signal "1" are recorded respectively for 9 seconds and 1 second. However, when these signals are erased, they are erased in such a manner that the recorded position in which the identifying signals are set at "1" is first searched and then a signal "0" is written over that position.
It is necessary to know the tape positional information when a tape is repeatedly reproduced to record the control signals and erase the identifying signal, as described above.
There are methods of detecting the tape positional information as follows:
(1) Providing on a reel base a frequency generator (FG), the rotational information of which is used to obtain the tape positional information;
(2) Recording a time code in an optional portion of PCM-ID; and
(3) Recording an identifying (ID) signal in a data portion of the sub-code area.
However, the method (1) is not exact because it is not easily analyzable, the method (2), because it is against the format rule, can be applied only to special tapes, and the method (3) has the possibility that a portion of the identifying signal can remain unerased.